[time-nuts] locking oscillators - an increase in power and/or stability ?
johncroos at aol.com
johncroos at aol.com
Sat Oct 11 20:13:36 UTC 2014
Perhaps this is useful
Microwave oscillators will change in both power output and frequency as a function of
the load impedance. This was first used to characterize magnetrons and klystrons. When
plotted on a Smith Chart it is called a Rieke Diagram. I later used it with Gunn Diodes.
You can make a considerable difference in the power output and immunity to load pulling
of the frequency by adjusting the output coupling from the waveguide cavity. I used thin
irises of varying diameter inserted between waveguide flanges to do this easily. When the power is greatest, the load pull is worst. If you provide a perfect match with a slide screw
tuner, you get all the power you can, and then there is not enough left in the cavity to sustain oscillation. Guess what - it stops.
I believe what you are seeing can be explained by the differing effects of changes in load impedance upon the oscillators. These will always be present of with any form of summing
device unless a ferrite isolator with a very high degree of isolation (40+ dB) is used on each source before the summing device.
john c roos k6iql
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Today's Topics:
1. locking oscillators - an increase in power and/or stability ?
(cdelect at juno.com)
2. Re: locking oscillators - an increase in power and/or
stability ? (Dr. David Kirkby (Kirkby Microwave Ltd))
3. Re: Digital Mixing with a BeagleBone Black and D Flip Flop
(Simon Marsh)
4. Re: HP10811-60212-B Pinouts. (dan at irtelemetrics.com)
5. Re: GPS jump (Jim Lux)
6. Re: locking oscillators - an increase in power and/or
stability ? (Jim Lux)
7. Re: HP10811-60212-B Pinouts. (Bob Stewart)
----------------------------------------------------------------------
Message: 1
Date: Sat, 11 Oct 2014 09:00:28 -0700
From: <cdelect at juno.com>
To: time-nuts at febo.com
Subject: [time-nuts] locking oscillators - an increase in power and/or
stability ?
Message-ID: <AABLDUXDNAHW5TK2 at smtpout02.dca.untd.com>
Content-Type: text/plain; charset=us-ascii
Came across this.
Might be relevant.
Cheers,
Corby
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930008868.pdf
a) Greater than 100% power combining efficiencies have been realized as
predicted. This implies that the output power from the combiner is
typically greater than
the sum of the power available from individual devices.
------------------------------
Message: 2
Date: Sat, 11 Oct 2014 17:41:12 +0100
From: "Dr. David Kirkby (Kirkby Microwave Ltd)"
<drkirkby at kirkbymicrowave.co.uk>
To: Discussion of precise time and frequency measurement
<time-nuts at febo.com>
Subject: Re: [time-nuts] locking oscillators - an increase in power
and/or stability ?
Message-ID:
<CANX10hDwPKRJUaChZbd1r3hDqVwhwo5ezQ1YKvPysUHdAKHoYw at mail.gmail.com>
Content-Type: text/plain; charset=UTF-8
On 11 Oct 2014 16:25, "Didier Juges" <shalimr9 at gmail.com> wrote:
> If I could get 1200W by combining two 300W amplifiers, I would now be
retired and very wealthy indeed.
>
> Unfortunately, there is no free lunch and unless somehow the Gun
oscillators were delivering more power when connected to the magic T (maybe
because of better matching) than when measured individually, combining two
X W sources will only give you, at best, 2xX W, or 3dB more power.
I see you don't get something for nothing - we are not taking about
perpetual motion.
I can see a few possible explanations.
1) Instrumentation error.
2) Better match - but that seems unlikely as I would have expected people
to have tried countless way to improve that.
3) Injection locking causes the Gunn diode to oscillate in a different way,
perhaps using different energy levels in the doped semiconductor.
The fact that they have become frequency locked, indicates that their mode
of operation has changed - they are not operating in the way the text books
say that they do.
About 2 decades ago I did an MSc in microwaves & optoelectronics. At that
time I had a pretty good understanding of how Gunn diodes worked, but I
have since forgotten the details. But it doesn't seem totally impossible
that the mode of operation changes to one which is more efficient.
> It does not matter what the combining structure is, magic T, coupler or
else.
I understand what you are saying, but it is hard to dismiss the possibility
it is true given several people have observed this. Just because it doesn't
fit into our established theories, doesn't mean it can not happen.
It is not breaking any laws of physics - the overall efficiency is well
below 100%.
> Didier KO4BB
Dave G8WRB.
------------------------------
Message: 3
Date: Sat, 11 Oct 2014 16:17:37 +0100
From: Simon Marsh <subscriptions at burble.com>
To: time-nuts at febo.com
Subject: Re: [time-nuts] Digital Mixing with a BeagleBone Black and D
Flip Flop
Message-ID: <54394A11.7090203 at burble.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
In this case, it seems reasonable that these multiple transitions are to
be expected as there isn't any filtering that takes place in hardware
prior to samples being captured by the BBB. The equivalent of the
filtering/zero crossing detection takes place in software in the edge
detection routine.
Cheers
Simon
On 11/10/2014 15:19, Bob Camp wrote:
> Hi
>
> If you are looking at the low frequency beat note out of a mixer and seeing
multiple transitions on an edge - you filtering or your limiter are not up to
the task. In most cases it’s the filter, but it can be either.
>
> Bob
>
> On Oct 11, 2014, at 9:10 AM, Robert Darby <bobdarby at triad.rr.com> wrote:
>
>> Simon,
>>
>> Welcome to the tangential world.
>>
>> I'm sure the clean edge I saw was an aberration, perhaps analogous to phase
locking in oscillators; I don't think it's desirable because common sense tells
you that with imperfect clocks and small phase differences there are bound to be
some number of glitches at each transition. I did nothing specific to eliminate
the glitches, it just happened that the positive going transition was very clean
but there's no reason I am aware of to suggest that one transition should be
better in this respect than another. Perhaps the flip flop I was using had a
shorter set-up time on negative to positive transitions than vice versa; the
smaller the set-up time the more likely one is to capture borderline events?
>>
>> I seem to recall that Didier Juges and Bruce Griffiths had some discussions
re DDMTD's (although I can't find it in the archives) but in any event you could
do far worse than dropping them a note directly to ask them about their thoughts
on the matter. I'm sorry I can't provide any analysis of your data; just not in
my skill set.
>> Perhaps Marcus or TVB could comment.
>>
>> Bob Darby
>>
>> On 10/10/2014 3:46 PM, Simon Marsh wrote:
>>> Bob,
>>>
>>> It's good to know someone else is trying this and it's not just me going off
on a tangent somewhere. I'd be very interested in understanding how you'd set
this up and how you'd got a nice clean rising edge.
>>>
>>> My understanding is that the 'glitches' occur because the clocks are being
sampled at a higher resolution than the cycle to cycle noise inherent in both
the clocks and the setup. Certainly, I don't expect any of the oscillators I
have available to be perfectly stable at ~1E-12 resolution, I'm sure they are
all over the place The clock phase noise shows up as fast transitions near the
actual beat edge as the clocks wander backwards and forwards over a few cycles.
I'm sure analysis of the glitches themselves would probably say quite a lot
about the cycle to cycle noise.
>>>
>>> I've attached an example of the transitions near an edge for a random TCXO.
The edge goes from 0 at the start to 1 at the end and shows noise over about 180
samples (@10mhz). This corresponds to about ± 5E-11. The crossing line of the
zero & one counts is where the edge is measured from the software point of view.
± 50ps sounds high to me, but I'm open to views as to whether that seems
reasonable or just shows my shoddy setup ?
>>>
>>> For fun, also attached is plot of the transitions for a UBLOX8 GPS module
outputing 10mhz. Compared to the TCXO that has about 10k transitions in a
second's worth of data, the UBLOX module has over 1.3M (this is with a beat
frequency of ~60hz). I think this is down to how the gps module is
inserting/removing cycles to get 10mhz from its internal clock frequency (as has
been discussed on here recently).
>>>
>>> Unfortunately, I don't have any expensive counters, that's part of my
motivation for doing this, so I'm interested in ways that I can understand the
noise floor.
>>>
>>> I tried passing one clock through a 74AC hex inverter and then measuring the
phase between the inverted/non-inverted signals on the basis that this should be
more or less constant and what I'd be measuring was noise. It's certainly a good
way of measuring how long the wire was that I used to make the connection This
seems to yield an ADEV of 5.92E-11 @ 1 sec, plots also attached.
>>>
>>> Interestingly the phase seems to drift over the measurement interval, I'm
open to suggestions on this, but guess this may be temperature related ? (open
on bench, non-airconditioned etc)
>>>
>>> If the plots don't come through as attached, they are also on google drive
here:
>>>
>>> https://drive.google.com/open?id=0BzvFGRfj4aFkSEdYV3lXcmZIVTA&authuser=0
>>>
>>> Cheers
>>>
>>>
>>> Simon
>>>
>>> On 10/10/2014 02:01, Robert Darby wrote:
>>>> Simon,
>>>>
>>>> I breadboaded a set-up in March using 74AC74's and two 10 MHz Micro Crystal
oscillators (5V square wave), one as the coherent source and one as the 10Hz
offset clock. I had no glitch filtering as described in the article you cite
(CERN's White Rabbit Project, sub nanosecond timing over ethernet) but found the
positive zero crossing was very clean. The negative crossing not so much; no
idea why one edge was clean and the other not. To ensure I only measured the
rising clock edge and not the noise on the falling clock, I programmed ATiny's
(digital 555?) to arm the D-flops only after a period of continuous low states.
>>>>
>>>> In any event, the lash up, as measure by a 5370, produced a clean linear
noise floor of 8e-12 at 1s. I regret to note that's very slightly better than my
results from the Bill Riley DMTD device. That's an indictment of my analog
building skills, not his design. It's also nicely below a 5370 on it's own and
needs only a simple 10 MHz counter for output. The zero crossing detectors for
sine wave oscillator input will perhaps be more critical.
>>>>
>>>> This was encouraging enough that I thought I'd try to build an FPGA version
of the same. The DDMTD is temporarily on back burner while I try to get a four
channel 1ns resolution time tagger running on the FPGA to use with the DMTD.
Almost there. I look forward to hearing your results with the BBB; keep us
posted.
>>>>
>>>> Bob Darby
>>>
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------------------------------
Message: 4
Date: Sat, 11 Oct 2014 12:57:12 -0400
From: dan at irtelemetrics.com
To: time-nuts at febo.com
Subject: Re: [time-nuts] HP10811-60212-B Pinouts.
Message-ID: <20141011125712.w9onqzp56o8k0c4o at mail.irtelemetrics.com>
Content-Type: text/plain; charset=UTF-8; format="flowed"
Hi All,
Yeah, that's the oscillator. The cables match the connector labels on
the board. Same blue coax cables.
Anyway, as this unit is missing the external oven controller, Is anyone
aware of an aftermarket controller or a good reference for the
controller required? I'm sure one can always build a controller, but
buying something ready to go would be a better option!
Thanks!
Dan
> bob at evoria.net said:
> > I found a picture that looks like your OCXO on Brooke Clarke's website.
> > Maybe he has a schematic or pinouts for the oscillator.
> > http://www.prc68.com/I/Images/Z3805A07b.jpg More info here:
> http://www.prc68.com/I/Z3805A.html
>
> The Z3805A is very similar to the Z3801A
>
>
> Brooke:
> typo in http://www.prc68.com/Alpha.shtml
> Down at the bottom, the link to the Z3805A page goes to
> file:///C:/Webdocs_Hosted/I/Z3805A.html
------------------------------
Message: 5
Date: Sat, 11 Oct 2014 10:18:45 -0700
From: Jim Lux <jimlux at earthlink.net>
To: time-nuts at febo.com
Subject: Re: [time-nuts] GPS jump
Message-ID: <54396675.2030409 at earthlink.net>
Content-Type: text/plain; charset=UTF-8; format=flowed
On 10/11/14, 8:08 AM, Bob Camp wrote:
> Hi
>
> To the extent that anything *is* locked, it’s been done for a lot longer than
the 1980’s. Long before common view GPS, Loran-C observations (and corrections
via clock trips) were used. You can look at it as a PLL, just a *very* fancy one
with *very* long time constants.
>
> Bob
>
>
It also depends on whether you need "lock in real time" or "lock in post
processing".
VLBI is a good example of the latter, and was done in the early 70s to
determine the position of the moon rover, for example.
------------------------------
Message: 6
Date: Sat, 11 Oct 2014 10:22:55 -0700
From: Jim Lux <jimlux at earthlink.net>
To: time-nuts at febo.com
Subject: Re: [time-nuts] locking oscillators - an increase in power
and/or stability ?
Message-ID: <5439676F.6020002 at earthlink.net>
Content-Type: text/plain; charset=UTF-8; format=flowed
On 10/11/14, 9:00 AM, cdelect at juno.com wrote:
> Came across this.
> Might be relevant.
> Cheers,
> Corby
>
> http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930008868.pdf
> a) Greater than 100% power combining efficiencies have been realized as
> predicted. This implies that the output power from the combiner is
> typically greater than
> the sum of the power available from individual devices.
>
Those are Indium Phosphide Gunn Oscillators which are highly nonlinear
and have significant dynamic component to their Z.
So you can't expect all the usual combining rules (which are typically
based on constant impedances, etc.)
This might be one of those "optimize the dynamic match to suck more
power out of the device" kind of things.
------------------------------
Message: 7
Date: Sat, 11 Oct 2014 10:46:40 -0700
From: Bob Stewart <bob at evoria.net>
To: Discussion of precise time and frequency measurement
<time-nuts at febo.com>
Subject: Re: [time-nuts] HP10811-60212-B Pinouts.
Message-ID:
<1413049600.75123.YahooMailNeo at web142706.mail.bf1.yahoo.com>
Content-Type: text/plain; charset=us-ascii
Hi Dan,
Didier's site is back up and this should give you a start:
http://www.ko4bb.com/manuals/index.php?dir=05%29_GPS_Timing/Z3801/Z3801A_Schematic
Bob
________________________________
From: "dan at irtelemetrics.com" <dan at irtelemetrics.com>
To: time-nuts at febo.com
Sent: Saturday, October 11, 2014 11:57 AM
Subject: Re: [time-nuts] HP10811-60212-B Pinouts.
Hi All,
Yeah, that's the oscillator. The cables match the connector labels on
the board. Same blue coax cables.
Anyway, as this unit is missing the external oven controller, Is anyone
aware of an aftermarket controller or a good reference for the
controller required? I'm sure one can always build a controller, but
buying something ready to go would be a better option!
Thanks!
Dan
------------------------------
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